The invention relates to a brake disc for a motor vehicle having at least a brake disc chamber and a friction ring fastened thereto. The friction ring, by way of particularly six to twelve radially inward directed centering and/or fastening extensions, placed in the axial direction on the face side on centering attachments of the brake disc chamber, and is fixed on the brake disc chamber by way of fastening devices, particularly screws and/or rivets, extending in the axial direction.
Composite brake discs are known which have friction rings made of gray cast iron, connected with a brake disc chamber made of light metal. German Patent document DE 10 2009 017 234 A1 describes a brake disc constructed in such a fashion, where the friction ring and the chamber are joined by separate elements, such as pins, screws, etc. In this case, the brake disc chamber has a base,—the chamber disc—, a surrounding wall,—the chamber jacket—, and an edge—the chamber edge—and is made of an aluminum alloy. The friction ring is fastened to the chamber edge by way of fastening devices, such as screws and/or rivets, extending in the axial direction; specifically by way of centering and/or fastening extensions of the friction ring, which point inward from an inner diameter of the friction ring and are placed in the axial direction on the face side onto centering attachments of the chamber edge and are connected with the fastening devices.
Light metal and gray cast iron expand differently when heated. In addition, the brake disc chamber and the friction ring are heated differently during braking. As a result, depending on the heat input into the friction ring during the braking, tensions occur in the brake disc by way of the connection between the brake disc chamber and the friction ring.
It is an object of the present invention to provide a brake disc, mainly for a motor vehicle, which has a connection between the brake disc chamber and the friction ring, by which connection as few tensions as possible will build up in the brake disc during the braking.
According to the invention, this and other objects are achieved by a brake disc for a disc brake, which comprises of at least a brake disc chamber and a friction ring fastened thereto which, by way of particularly six to twelve centering and/or fastening extensions directed inward from its inner diameter, placed in the axial direction on the face side on centering attachments of the brake disc chamber, is fixed on the brake disc chamber by way of fastening devices, particularly screws and/or rivets, extending in the axial direction. The centering attachments of the brake disc chamber are recesses in the brake disc chamber edge or in the brake disc chamber edge and in the brake disc chamber jacket, one centering and/or fastening extension of the friction ring respectively projecting into them.
If the brake disc and the brake disc chamber are mutually separable parts, the manufacturing of each part will be simple and cost-effective. Furthermore, the brake discs can be exchanged without the necessity of demounting the entire wheel assembly, and weight is also saved. It is advantageous for the brake disc chamber to center the brake disc in the radial and axial direction. When the friction ring is guided by way of its centering and/or fastening extensions in grooves of the brake disc chamber and is not connected directly with the latter by way of fastening devices, this has the advantage that, when heated, the friction ring and the brake disc chamber can expand relative to one another to a certain extent, without the occurrence of significant material tensions because of a different expansion.
In an advantageous embodiment of the invention, the brake disc is characterized in that, by way of the fastening devices, a fastening ring is mounted at the brake disc chamber edge. The fastening ring covers the recesses in the brake disc chamber edge and thereby fixes the centering and/or fastening extensions of the friction ring at least in the axial direction at the brake disc chamber.
As a result, the brake disc chamber and the friction ring are advantageously fixed to one another such that heat expansion movements, as a result of different materials, can still take place without causing excessive material tensions because of the fastening by way of balancing features of the fastening device. For this purpose, it is also advantageous for the centering and/or fastening extensions of the friction ring to form a clearance fit in the circumferential direction with the recesses in the brake disc chamber. This also facilitates the joining of the brake disc chamber and the friction during the mounting of the brake disc. When the recesses in the brake disc chamber in the axial direction are then less deep, particularly by 0.1 to 0.8 mm, than the depth of the centering and/or fastening extensions in the axial direction, the fastening ring will become wavy during the connection with the brake disc chamber as a result of the depth difference of its supporting surfaces. On the one hand, this causes the connection of the brake disc chamber and the friction ring to be free of play in the axial direction and, on the other hand, causes it to be flexible because of the elasticities of the material.
An embodiment of the invention is particularly simple for the mounting of the brake disc, in which the brake disc centering device and/or the brake disc fastening device is constructed on the brake disc chamber jacket profiles, situated on the exterior side in the axial direction, on one side, and the chamber disc is constructed on the other side; i.e. viewed from the friction ring, the brake disc chamber extends essentially in one direction. In this case, the brake disc chamber jacket may extend as a cylinder jacket parallel to the center axis of the brake disc chamber parallel to the center axis of the brake disc chamber or may be constructed in a beveled fashion as a conical jacket.
When then the one-piece internally cooled friction ring of the brake disc consists of two friction discs with cooling-air ducts, which connect the latter and are situated in-between, and when the centering and/or fastening extensions are situated on only one friction disc, particularly on that friction disc which faces the brake disc chamber, this has the advantage that the cooling of the friction ring is less affected by the brake disc chamber.
Furthermore, the brake disc chamber jacket can be reinforced at least by a chamber disc extending in the radial direction, which is situated at the end of the brake disc chamber jacket further away from the friction ring. In this case, the brake disc chamber jacket and/or the chamber disc will then consist of a light metal alloy and can both advantageously be cast together in one operation. In comparison to the gray cast iron material, the weight can thereby be reduced enormously.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.